Impact of Heat Stress on Growth and Fodder Yield of C3 (Cowpea) and C4 (Pearl Millet) Crops: Insights From Field and Modelling Experiments

Rising temperature is a major concern globally and its impact on crop production and food security is obvious. The impact of rising temperature on various crops needs to be studied under field conditions. Therefore, a study was conducted at Ludhiana (India) during 2021 and 2022 to investigate the effect of high temperature on growth and yield of cowpea (Vigna unguiculata (L.) Walp.), a C3 legume, and pearl millet (Pennisetum glaucum (L.) R. Br.), a C4 cereal grown as fodder crops. Artificial heat stress was imposed during 0–15, 16–30, 31–45, 46–60 and 0–60 days after sowing (DAS). Mini heat tents made up of galvanised iron pipe and polythene sheets were installed which resulted in an increase in maximum and minimum temperature by 4.0°C–5.1°C and 0.5°C–1.5°C, respectively. The heat stress resulted in a statistically significant reduction in the number of branches, plant height, dry matter and fresh fodder yield of cowpea, while it resulted in a statistically significant increase in plant height, dry matter and fodder yield of pearl millet. Physiological parameters like chlorophyll index and flavanol index were decreased under high temperature in both crops indicating stress. Heat stress positively affected chlorophyll fluorescence in pearl millet and negatively in cowpea. Green fodder yield of cowpea decreased by 3.83%–18.56%, while that of pearl millet increased by 9.44%–25.02% under different heat stress treatments. Thus, heat stress resulted in a decrease in fodder productivity of the C3 crop due to a reduction in physiological and growth parameters, while the increase in the same led to an improvement in fodder productivity of the C4 crop.